SILTUXIMAB MAY CAUSE CYP450 ACTIVITIES TO HIGHER LEVELS LEADING TO INCREASED METABOLISM OF DRUGS THAT ARE CYP450 SUBSTRATES COMPARED TO METABOLISM PRIOR TO TREATMENT WITH SILTUXIMAB. UPON INITIATION OR DISCONTINUATION OF SILTUXIMAB, IN PATIENTS BEING TREATED WITH CYP450 SUBSTRATES WITH A NARROW THERAPEUTIC INDEX, PERFORM THERAPEUTIC MONITORING OF EFFECT (E.G., WARFARIN) OR DRUG CONCENTRATION (E.G., CYCLOSPORINE OR THEOPHYLLINE) AS NEEDED AND ADJUST DOSE. THE EFFECT OF SILTUXIMAB ON CYP450 ENZYME ACTIVITY CAN PERSIST FOR SEVERAL WEEKS AFTER STOPPING THERAPY. EXERCISE CAUTION WHEN SILTUXIMAB IS CO-ADMINISTERED WITH CYP3A4 SUBSTRATE DRUGS WHERE A DECREASE IN EFFECTIVENESS WOULD BE UNDESIRABLE (E.G., ORAL CONTRACEPTIVES, LOVASTATIN, ATORVASTATIN).
DO NOT ADMINISTER LIVE VACCINES TO PATIENTS RECEIVING SILTUXIMAB BECAUSE IL-6 INHIBITION MAY INTERFERE WITH THE NORMAL IMMUNE RESPONSE TO NEW ANTIGENS.